In Vivo Tibial Loading of Healthy and Osteolathrytic Mice

Abstract

Although the in vivo tibial loading model has been used to study the bone forma- tion response of mice to exercise, little emphasis has been placed on the translation of architectural and compositional modifications to changes in mechanical behaviour. The goals of the studies discussed below were to investigate the mechanical response in both healthy and osteolathrytic mice to this loading model and to determine the dose-depended effects of strain level on these properties. In two separately designed studies, strain levels ranging from 1700 to 2400 were applied to the right tibiae of 8 week old female C57BL/6 mice, while the left tibiae were used as non-loaded control. The first study consisted of loading both PBS- and BAPN-injected mice to 1750 microstrain which resulted in little bone formation but some tissue-level changes in mechanical analyses and an improvement in fatigue-resistance in terms of microdamage accumulation. The second study loaded healthy mice to three strain levels (1700, 2050, and 2400). Results indicated that the low end of the strain range did not engender a robust formation response, while the high end of the strain range resulted in a woven bone response in half of the animals in that group. Future studies will focus on the mid-strain level of 2050 which induced both significant architectural and mechanical improvements.